Begin by bringing a large pot of salted water to a rolling boil over high heat. Add the rigatoni pasta and cook according to package instructions until al dente, about 10-12 minutes. Drain and set aside.

In a large skillet, heat the olive oil over medium heat. Once shimmering, add the Italian sausage, breaking it apart. Cook until browned and crispy, about 5-7 minutes.

Add the diced onion and minced garlic to the skillet. Sauté until the onion is translucent and fragrant, about 3-4 minutes.

Pour in the crushed tomatoes, heavy cream, and chicken broth. Stir to combine and season with Italian seasoning, red pepper flakes, salt, and pepper. Let simmer for about 10 minutes.

Add the drained rigatoni to the skillet. Stir to coat the pasta with the sauce and cook for another 2-3 minutes.

Sprinkle the grated Parmesan cheese over the pasta and stir until melted and creamy.

Remove from heat and serve hot, garnishing with fresh basil leaves.